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Centrifugal Nuclear Thermal Propulsion is a second-generation propulsion concept currently being researched to succeed traditional solid core nuclear thermal propulsion. Current efforts across the space industry are focusing on development of technologies for enabling manned flight to Mars and scientific missions to the outer planets. To enable these types of mission's direct injection trajectories are needed to decrease exposure to astronauts and scientific payloads to the harsh environment of space. Current efforts in nuclear thermal propulsion have shown great promise in higher specific impulses ∼900 s, but even these levels of specific impulse fall short for manned Mars missions with durations less than two years or direct injection to orbit of the outer ice giants Uranus and Neptune without the use of gravity assists. High performance nuclear thermal propulsion has been proposed using bubble through nuclear reactors to reach specific impulses as high as 1800 s, however significant challenges exist to prove the feasibility of such a system. One of the major challenges is the fluid mechanics within the core of the engine since little is known about uranium in the liquid phase. An experimental study has been conducted to better understand the fluid dynamics to better inform the thermodynamic and nucleonic models. Using the data from the experiment, high-fidelity simulations have been developed to predict the fluid dynamics of the uranium fuel. This information can then be further fed into thermodynamics models in development to predict core temperatures and system behaviour. The validated models show that small bubbles reach thermal equilibrium, and high centrifugal forces and surface tension assist in confining the molten uranium within the reactor core. Injector methods suggest feasible configurations to encourage bubble flow while minimizing backflow of the propellant, motivating further study of Centrifugal Nuclear Thermal Propulsion based systems. • Galinstan (Ga67In20.5Sn12.5) was determined to be a suitable uranium simulant for bubble formation. • High Speed Radiography was used to determine bubble characteristics using machine learning algorithm. • Hydrogen bubbles in uranium rapidly reach local equilibrium with diameters of 0.266 mm and reaching velocities of 16 m/s. • To date all research indicates that a centrifugal nuclear thermal rocket is feasible. [ABSTRACT FROM AUTHOR]

The non-equilibrium spectra of shock-heated nitrogen in the UV-visible range are investigated in a detonation driven shock tube. Spectral identification indicates that the main contributors to the spectra are molecular radiation of N 2 (2+) and N 2 + (1-). Vibrational and rotational temperatures of N 2 (C) and N 2 + (B) are determined through spectral fitting. The post-shock spectra of pure nitrogen are obtained for shock velocities ranging from 6.82–9.00 km/s and P 0 = 30–200 Pa at the shock arrival time. Differences between vibrational and rotational temperatures of N 2 (C) and N 2 + (B) are observed, suggesting that nitrogen is in a non-equilibrium state at shock arrival moment. Time-resolved spectra are obtained within varying delay times of 0– 2. 0 μ s at P 0 = 200 Pa and shock velocity of V sw = 6.60 km/s. Time-resolved temperatures are determined to illustrate the time-resolved non-equilibrium characteristics of nitrogen at high temperature. It is observed that the non-equilibrium characteristics of nitrogen gradually weaken with increasing time and the thermal equilibrium was not obtained within 2. 0 μ s. Finally, the time-resolved temperatures are compared with CEA (Chemical Equilibrium with Applications) prediction, revealing that the difference in temperature between the experiment and the CEA equilibrium calculation decreases as time increases. • The radiative spectra of nitrogen are obtained in shock tube with shock velocity of 6.5–9.0 km/s. • The shock velocity-dependent non-equilibrium characteristics of nitrogen are revealed. • The time-resolved non-equilibrium characteristics in the post-shock region are studied. • The non-equilibrium effects of N 2 (C) and N 2 +(B) are obtained and analyzed. [ABSTRACT FROM AUTHOR]

Mullite fiber-based porous ceramics is one of the most commonly used high-temperature insulation materials. However, how to further reduce the thermal conductivity and improve the strength of such materials has been a challenge in the field of high-temperature insulation. In this paper, mullite micro/nano fiber-based porous ceramic was prepared by introducing mullite nanofibers into mullite microfiber-based porous ceramics and the effect of microfiber/nanofiber weight ratio on the samples properties were characterized and analyzed. Results showed that the compressive strength and high-temperature thermal insulation properties of the porous ceramics increased significantly with an increase in the nanofiber content. For the porous ceramics with similar density (about 0.50 g/cm3), the compressive strength of the sample with a microfibers/nanofibers weight ratio of 1:2 was 1.43 MPa, which was much higher than that of the porous ceramics prepared with only microfibers (0.26 MPa). Meanwhile, the backside thermal equilibrium temperature of the sample with a microfiber/nanofiber weight ratio of 1:2 at 900 °C environment was 355.8 °C, which was much lower than that of the porous ceramic prepared with only microfibers (476.5 °C). In addition, in order to investigate the temperature resistance of mullite micro/nano fiber-based porous ceramics, the sintering temperatures was increased from 1400 °C to 1500 °C. Results shows that the high-temperature thermal insulation performance of mullite micro/nano fiber-based porous ceramics with high mullite nanofiber content decays more seriously. The back-temperature test showed that the thermal equilibrium temperature of the samples with a mullite micron/nanofiber weight ratio of 1:1 in 900 °C environment increased rapidly from 386.3 °C to 454.2 °C when the sintering temperature was increased from 1400 °C to 1500 °C. The preparation of mullite micro/nanofiber-based porous ceramics provides a new strategy to improve the performance of fiber-based porous ceramics. [ABSTRACT FROM AUTHOR]

Shock/shock interactions (SSIs) often lead to high thermal loads. To understand the influences of thermochemical non-equilibrium effects on the Type III SSI, four gas models based on the assumption of thermal perfect gas (TPG), thermal equilibrium chemical non-equilibrium gas (TECNG), thermal non-equilibrium chemical frozen gas (TNCFG), and thermochemical non-equilibrium gas (TCNEG) are employed to simulate the Type III SSI at Mach 10. The intersection of incident shock and bow shock is determined by dimensionless intercept of 0.05 and 0.1. It is found that the chemical non-equilibrium effects significantly lift up the impingement position of shear layer by reducing the standoff distance of bow shock. As a result, the peaks of wall pressure and heat flux calculated by TECNG and TCNEG model are higher than TPG and TNCFG model, respectively. Type IIIa SSI occur in the flows calculated by the TECNG and TCNEG model for the case with a dimensionless intercept of 0.1. The peaks of wall pressure and heat flux calculated by TECNG model are both over four times higher than those of TPG model. The thermal non-equilibrium effects slightly increase the standoff distance of bow shock and lower the impingement position of shear layer. In addition, the thermal non-equilibrium reduces the angle to the horizontal direction of shear layer by increasing the specific heat ratio. • Type III shock/shock interaction at Mach 10 are simulated by four gas models. • The influences of non-equilibrium effects on flow fields are analyzed. • The chemical non-equilibrium effects significantly increase the peak values of heat flux and pressure. • The mechanisms of non-equilibrium effects on peak heat flux and pressure are revealed. [ABSTRACT FROM AUTHOR]

To characterize the impact of thermal nonequilibrium conditions in shock-induced combustion in high Mach number scramjet engines, a comparative numerical investigation has been performed. The combustor configuration was based on the HyShot II scramjet while the total enthalpy is 3.3 MJ/kg which resembles Mach 8 flight condition. The improved delay detached eddy simulation with Park two-temperature approach in combination with the vibration-chemical coupling model was employed in the nonequilibrium simulations. It is shown that under thermal nonequilibrium inflow conditions, noticeable stratification in the thermal state exists in the circumferential direction both in the combustor section and exhaust nozzle. In the inner core where the fuel mixes with the mainstream, flow deceleration caused by the heat release leads to a sufficient transformation of energy between the vibrational and translational-rotational modes approaching the thermal equilibrium state. However, the τ v , m i x is quite large in the supersonic mainstream, whereby the thermal nonequilibrium dominates. For the case with higher T v in the inflow, the fuel jet's penetration height is lower while the local viscosity is higher which results in poor mixing between the fuel and air stream. Nevertheless, a 400 K increase in inflow T v gives a higher effective temperature, which promotes the dissociation reactions, shortens the ignition distance and yields an 8% increase in the overall combustion efficiency. With better combustion performance, an additional 6% deceleration in the supersonic mainstream and the energy exchange rate between vibrational and translational-rotational modes becomes almost four times faster at the combustor outlet, which promotes the restoration of the thermal equilibrium state. Furthermore, under higher inflow vibrational temperature, the shock-induced combustion in supersonic crossflow becomes less stable with noticeable fluctuations in combustion heat release and local static pressure. • Combustion dynamics for the Hyshot II scramjet engine under different thermal nonequilibrium inflow conditions were investigated numerically. • Noticeable stratification in thermal state in the circumferential direction was observed when vibrational nonequilibrium effect was considered. • Increase in vibrational temperature at combustor inlet by 400 K resulted in an 8% increase in the overall combustion efficiency. • The instability of shock-induced combustion was enhanced under higher inlet vibrational temperature. [ABSTRACT FROM AUTHOR]

Recently, nanoscale thermometry has attracted extensive attention. Here, we present an innovative approach to enhance the sensitivity of upconversion nanoparticles for thermometry through near-field manipulation. This method involves a composite structure consisting of photonic crystals and upconversion nanoparticles, with the near-field of the nanoparticles manipulated by tuning the absorption of the photonic crystals. The fluorescence intensity ratio (540nm/520 nm) of 4H 11/2 and4S 3/2 states of upconversion nanoparticles doped with Er3+ ions is sensitive to temperature change and employed as a temperature indicator that satisfies Boltzmann thermal equilibrium. The composite structure exhibited a relative thermometry sensitivity of 21.9 × 10−3 K−1 at 298 K, representing a significant improvement over pure core-shell upconversion nanoparticles with a 63.43% increase in relative sensitivity and a 675% increase in absolute sensitivity. This finding demonstrates the potential of our approach for advancing nanoscale thermometry. [ABSTRACT FROM AUTHOR]

This paper explores thermal quantum memory-assisted entropic uncertainty, Bell-non-locality, and entanglement in a two-qubit Heisenberg XXX chain with x -directional Dzyaloshinskii-Moriya (DM) and Kaplan-Shekhtman-Entin-Wohlman-Aharony (KSEA) interactions in thermal equilibrium. We find this crucial that the initial degree of nonlocality and entanglement in the two-qubit state entirely depends upon the temperature, orientation, and strength of the DM and KSEA interaction of the magnetic field. Among many other situations, the magnetic field characterized by DM interaction with minimal temperature, exchange coupling strength, and KSEA interaction is the most reliable for generating and maintaining maximal nonlocality and entanglement while completely suppressing entropic uncertainty. On the other hand, repeated revivals and non-Markovian dynamics have been observed when the magnetic field is characterized by exchange coupling constant, DM and KSEA interaction with a higher temperature limit. Except for temperature-based magnetic fields, we show that maximal entanglement and nonlocality are generated and preserved in the two qubits with zero-order entropic uncertainty, which we believe is a better result than previous studies. [ABSTRACT FROM AUTHOR]

The prime motive of this disquisition is to scrutinize simultaneous aspects of external forcing mechanism and internal volumetric forces on non-Newtonian liquid filled in square enclosure. Inertially driven upper lid is assumed by providing constant magnitude of slip velocity whereas thermal equilibrium is disturbed by assuming uniform temperature at lower boundary and by keeping rest of walls as cold. To enhance thermal diffusion transport with in the flow domain cold as well as adiabatic temperature situation is provided. In view of velocity constraints all the extremities at no-slip except the upper wall which is moving with U Lid . Formulation is attained in dimensional form initially and afterwards variables are used to convert constructed differential system into dimensionless representation. A numerical solution of leading formulation is sought through Galerkin finite element discretization. Momentum and temperature equations are interpolated by quadratic polynomials whereas pressure distribution is approximated by linear interpolating function. Domain discretized version is evaluated in view of triangular and rectangular elements. Newton's scheme is employed to resolve the non-linearly discretized system and a matrix factorization based non-linear solver renowned as PARADISO is used. Validation of results is ascertained by forming agreement with existing studies. In addition, grid independence test is also performed to show credibility of performed computations. Stream lines and isothermal contours patterns are portrayed to evaluate variation in flow distributions. Kinetic energy and local heat flux for uniform and non-uniform heating situations are also divulged in graphical and tabular formats. Increase in Reynold number produces decrease in kinetic energy of fluid. Enhancement in Grashof number causes enrichment of thermal buoyancy forces due to which Nusselt number uplifts. Clock wise rotations increase against upsurge in magnitude of Reynold number which is evidenced form stream lines. Squeezing of secondary vortex against Prandtl number arises due to dominance of viscous forces. [ABSTRACT FROM AUTHOR]

Aero-thermal analysis of hypersonic vehicles is of fundamental interest for structural design and material selection. Therefore, we investigated the aerodynamic heating characteristics of a blunt cone made from stainless steel in a combustion-heated hypersonic wind tunnel with a free stream of Mach 6. During ground testing, the temperature rise of the model from room temperature to thermal equilibrium under the influence of hypersonic flow was measured with thermocouples, and the equilibrium temperature of the blunt section was 1130–1150 K. In addition, the transient thermal response of the model to the aerothermodynamic load was simulated by fluid-thermal coupled analysis and compared with the measurement data. The obtained results correspond well to typical thermocouple data, and the temperature predicts the measurement with an accuracy on the order of 8.8%. On this foundation, some factors affecting the radiation equilibrium temperature of the blunt cone are also discussed. The analysis indicates that emissivity has an important influence, while turbulence intensity at the nozzle inlet has minimal impact. • The effective experimental time reached 350 s, and the radiation equilibrium temperature of the cone section is obtained in 225 s. • Under the experimental conditions of Mach 6 and total temperature of 1712 K, the radiation equilibrium temperature of the cone section is 1130–1150 K. • The fluid-thermal coupling analysis method can effectively predict the thermal response process of the model. • The radiation equilibrium temperature in the blunt section is not sensitive to the change of the total temperature of the gas flow. • Surface emissivity has a great influence on the radiation equilibrium temperature, while the turbulence intensity gives the minimal impact. [ABSTRACT FROM AUTHOR]

• DUGKS is extended to moving boundary rarefied gas flows with heat transfer. • The complex advancing boundary condition is handled by the IB method. • Least square method is applied to the information construction at the ghost cell. • Six flow problems are performed to test the versatility of the method. Rarefied gas flows in complex geometries with heat transfer and moving boundaries have received remarkable attention due to the prevailing of micro/nano science and engineering applications. This study presents an immersed boundary (IB)-based discrete unified gas kinetic scheme (DUGKS) for the simulation of complex moving boundary thermal rarefied flows. The fluid and temperature fields are solved according to the DUGKS with Shakhov collision model (SDUGKS), which is capable of modeling non-unit Prandtl number problems in all Knudsen regimes. The IB approach, featured by its superior performance to incorporate complicated boundary constraints on Cartesian grids, is applied here to handling the interaction between the micro gas and curved boundaries. Specifically, for the IB adopted in this study, we use the least square method for the reconstruction of the distribution functions near the boundary. The accuracy of the IB-SDUGKS is explored comprehensively in six benchmark problems, including the micro lid-driven cavity flow, thermal equilibrium gas in a circular domain, thermal transpiration in an enclosure, moving shuttle in a rarefied gas, movement of a piston with pressure differences and particle free motion in a lid-driven cavity. The present results agree well with the corresponding analytical and direct simulation Monte Carlo (DSMC) solutions, illustrating the versatility of the present IB-SDUGKS complex thermal rarefied flows. [ABSTRACT FROM AUTHOR]

• The melting behaviors under four different strengthening structures are compared. • The finned metal foam tube under steady rotation realizes the best performance. • The effect of fin type, graded porosity, and rotational speed are further analyzed. • A maximum 46.68% melting time reduction is realized under the optimal structure. The latent heat thermal energy storage (LHTES) technology based on solid-liquid phase change material (PCM) is of great significance for the efficient utilization of thermal energy. To address the issues of slow thermal response and non-uniform melting of the LHTES technology, a hybrid heat transfer enhancement method combined with finned metal foam and steady rotation is proposed in this work. An enthalpy-porosity model considering non-Darcy porous effects and mechanical rotation is established based on the local thermal equilibrium assumption and the fixed grid system. Four different structures (uniform metal foam, graded metal foam, finned metal foam with uniform porosity, and finned metal foam with graded porosity) are investigated firstly to identify the optimal structural arrangement under the same volume of PCM. Numerical results demonstrate that the LHTES units strengthened by the finned metal foam with graded porosity achieve the shortest melting time and largest thermal energy storage rate (TESR). The graded porous structure reduces thermal resistance, rotation enhances flow and heat transfer inside the container, and the fins expand the heat source area. Moreover, the effect of different fin types, graded porosities, and rotational speeds are further considered. The findings suggest that the increase of these three parameters does not correspond to better thermal performance; instead, there is an optimal value. Compared with the base case, the optimal configuration (fin length of 20 mm, fin width of 1.5 mm, porosity gradient of 2%, and rotational speed of 0.5 rpm) can shorten the melting time by 46.68%, increase the TESR and Nu by 74.06% and 69.02%, respectively. This paper validates the feasibility of the hybrid heat transfer enhancement method with finned metal foam and steady rotation, which can offer new insights into the engineering practice of the LHTES technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Current intensity, current density and resistance voltage under thermal equilibrium are considered. • Studied the influence of various electrode structural parameters on the performance of the electrolysis cell. • Compared multiple optimization algorithms to verify the reliability of the obtained Pareto frontier distribution. • Utilized NSGA-II for multi-objective optimization of the Multipolar electrolysis cell. • Reduced electrolysis cell resistance voltage, enhanced current density. In the operation of industrial multipolar magnesium electrolysis cell, cell voltage and current density are important indicators of the production performance of the cell, while thermal balance is a key factor for normal operation. This paper utilizes the finite element method to establish a three-dimensional full cell thermal-electric model, studying the thermal field distribution and current density distribution in a 165kA multipolar magnesium electrolysis cell. Based on the heat balance of the multipolar cell, the influence of structural parameters on current intensity, average current density at the anode surface and resistance voltage is assessed. Dimensionless analysis yielded optimization criteria, and the Non-dominated Sorting Genetic Algorithm II (NSGA-II) was employed for multi-objective optimization problems. When stringent optimization is executed, significant performance improvements can be achieved in terms of the electrolysis cell's resistance voltage and current density. Moreover, under the optimization criteria, the relative error of the 265kA multipolar magnesium electrolysis cell model is less than 1 %. The results indicate that the workflow combining the finite element method with multi-objective optimization algorithms can be applied to the optimization and scale-up design of high-current multipolar magnesium electrolysis cell. [ABSTRACT FROM AUTHOR]

• Decreasing the production of CO 2 and tar in biomass gasification. • Effect of CaO carbonation heat release on biomass gasification to hydrogen. • Reducing O 2 consumption for biomass gasification in self-heating systems. • Obtaining hydrogen-rich syngas. In pine chips gasification experiment, at 700 °C and 15 % H 2 O, with the mass ratio of Ca 90 Fe 10 /B to 1.5, the H 2 yield is 210.50 mL/g. The H 2 yield improves by 2.39 times and the tar yield decreases by 16 % compared to without CaO. In the pine chips gasification simulation with the system's own thermal equilibrium, at 700 °C, the heat release of Ca 90 Fe 10 adsorption of CO 2 is 56.91 MJ/h for Ca 90 Fe 10 /B mass ratio of 1.5, and the required O 2 inflow is 1.9 kg/h, the molar flow of H 2 is 0.58 kmol/h. To achieve material circulation, 0.5 kg/h of CH 4 is added to the calciner for combustion to satisfy heat absorption of CaCO 3 to regenerate CaO, which consumes 2.0 kg/h of O 2. The whole cycle O 2 consumption is 3.90 kg/h, which is 1.02 kg/h less than without CaO, and the H 2 yield has increased by 1.35 times. [ABSTRACT FROM AUTHOR]

• Wavy microchannel with compound rib of porous layer and solid wall is proposed. • The thermal-hydraulic performance is related to three types of structural parameters. • Multi objective genetic algorithm method is employed to optimize MCHS performance. • The 37.61% and 16.67% decreases in R and Ω with optimal compound rib compared to solid rib. The combining rib of porous layer and solid wall is set in wavy microchannel heat sink to enlarge heat transfer area and convection with smaller increase in flow resistance, in which the consumption of pump power relates to the ratios of wave amplitude to length or to width and the thickness of porous layer due to vortices generation while coolant passing through channel. The local thermal equilibrium occurs in porous layer, and the Forchheimer-Brinkman-Darcy relations were used to describe the flow inside porous ribs. The effects of channel-to-pitch width ratio, width ratio of porous layer to pitch and microchannel height on its cooling performance are investigated, and the parameter of figure of merit (FOM) is defined to evaluate thermo-hydraulic performance in wavy microchannel. Besides, the multi objective genetic algorithm method is employed to optimize structure parameters in wavy microchannel to obtain better performances, in which the increase in thermal resistance from 0.062 K/W to 0.166 K/W together with consumption of pump power decreasing from 0.00416 W to 0.00185 W can be obtained in the Pareto front set, and it relates to the heat dissipation in convection between coolant and bottom surface or vertical side ribs. Compared to wavy microchannel with solid rib, the 37.61% and 16.67% decreases respectively in thermal resistance and consumption of pump power occur in the case with optimal combining rib of porous layer and solid wall. [ABSTRACT FROM AUTHOR]

• Whole phase transition process of droplet at supercritical conditions was analyzed. • Classical, transitional and supercritical stage form whole phase transition process. • Interface deviates from global thermal equilibrium in transitional two-phase stage. • Miscible boundary layer in supercritical stage will replace non-continuum interface. • Pseudo-boiling occurs in miscible boundary layer containing supercritical fluids. With the development of heavy-duty diesel engines, the in-cylinder ambient conditions of the diesel engine are well above critical points of the main components of the diesel fuel. Therefore, significant changes arise in the phase transition process of the liquid fuels. However, the entire phase transition process of the liquid fuels in such supercritical environments is not well understood compared with that under subcritical conditions. In this work, A high-pressure transient droplet evaporation model was presented for the theoretical analysis of phase transition processes of the heptane/dodecane/hexadecane-nitrogen binary system under supercritical conditions. Analysis of the thermodynamic pseudo-trajectories reveals that the alkane droplets will undergo a three-stage phase transition process when the ambient condition is much higher than the critical point of alkanes, including classical two-phase mode, transitional two-phase mode, and supercritical single-phase mode. The evaporation dominates the phase transition process in the classical two-phase mode, and the transition from classical two-phase modes to transitional two-phase modes occurs when gas-liquid interfaces deviate from the global thermal equilibrium. In transitional two-phase modes, a gas-liquid interface still exists and separates the liquid phase and vapor phase, but with a questionable adoption of vapor-liquid equilibrium. The transition from the transitional two-phase mode to the supercritical single-phase mode occurs when the thermodynamic state of the binary mixture in the interface reaches the critical mixing state. We distinguished the phase states for the whole phase transition process according to the thermodynamic analysis of binary systems. Analogous to the immiscible interface in classical two-phase mode, a miscible boundary layer containing supercritical fluids exits between the liquid core and gas in the initial period of the supercritical single-phase mode. The pseudo-boiling phenomenon occurs in this boundary layer. [ABSTRACT FROM AUTHOR]

There are strong interests in hypersonic propulsion communities in predicting the flow and heat transfer characteristics over a hypersonic vehicle. However, this is quite challenging due to the emergence of thermal and chemical out-of-equilibrium effects as prominent in a high-temperature flow. In this work, we conduct 2D numerical investigations on the hypersonic double cone flow in a surrounding of the stagnation enthalpy of 15.23 MJ/kg by solving the laminar Navier–Stokes equation systems with the vibrational non-equilibrium processes and seven species air reactions. We then conduct the sensitivities analyses on the flow and heat transfer features, as different transport models and different thermochemical models are applied. It is shown that the aerodynamic heat is more sensitive to the transport models than the flow, and the transport coefficients computed by the Gupta-Yos model are more suitable for predicting the double cone flow at the high enthalpy. On the other hand, the flow field of the high enthalpy double cone is more sensitive to the thermochemical models than the heat transfer on the wall excluding the peak position. Behind the detached shock, chemical reactions are found to enhance thermal or vibrational out-of-equilibrium effects. However, vibrational non-equilibrium effects are revealed to weaken the degree of molecule dissociation reactions. Two flow separations occur in the flow field computed by using the thermal non-equilibrium gas models, but the flows of thermal equilibrium gas models separate only once. The maximum values of wall parameters without chemical reactions are found to deviate greatly from the experimental measurements. The thermochemical out-of-equilibrium gas model can predict the separation region size closer to the experiment than the two reported numerical results. The wall static pressure and heat flux are also shown to well match the experimental results. The present work should shed lights on better understanding thermochemical non-equilibrium effects of complex flow phenomenon like the shock wave/boundary layer interaction in hypersonic propulsion with high enthalpy surroundings. [ABSTRACT FROM AUTHOR]

The porous ribs and solid ribs paved with porous layer (combining ribs for short) on sidewalls are set respectively in upper and lower channels in double-layered microchannel heat sink (MCHS) with microencapsulated phase change material (MPCM) slurry as coolant to obtain better thermal performance. In the cases, more heat transfer occurs between coolant and solid ribs with MPCM slurry as coolant due to phase change in microencapsulate, and larger specific area in porous layer. The local thermal equilibrium is considered to be in porous layer, and the Forchheimer-Brinkman-Darcy relations were used to describe the flow inside porous ribs. The effects of porous layer, its thickness in combining ribs, channel-to-pitch width ratio and channel aspect ratio on heat transfer and hydraulic properties in channel with MPCM slurry as coolant are investigated. Besides, the heat flux from heating surface released through the upper channel or lower channel to the outside can be allocated with the channel-to-pitch width ratio, width ratio of porous layer to pitch in the lower channel, and channel aspect ratio in double-layered microchannel. The parameter of figure of merit (FOM) is defined to evaluate thermo-hydraulic performance. Compared to the case with copper solid ribs in lower and upper channels as benchmark (i.e. FOM = 1), the 14% and 124.56% higher FOM value occur in the cases respectively of solid and porous ribs, and combining and porous ribs in lower and upper channels, as well as the 18.93% and 65.96% decreases respectively in thermal resistance and pumping power in case of MPCM slurry as coolant with combining and porous ribs in lower and upper channels. The appropriate width ratio of porous layer to pitch and porosity in porous layer will benefit thermal behavior. [ABSTRACT FROM AUTHOR]

In this study, the thermal performance of triplex-tube heat storage system consisting of RT55 phase change material and Cu metal foam composite was investigated to find out the most efficient configuration among 17 distinct models (M1-M17) categorized into 4 distinct classes. Under simultaneous charging and discharging conditions, the melt fraction and latent heat storage capacity were calculated and finally an enhancement parameter was formulated. Additionally, the multi-criteria decision-making methods such as Analytical Hierarchy Process (AHP) and Technique for Order Performance by Similarity to Ideal Solution (TOPSIS) were employed to obtain preference-based optimized designs. The findings revealed that model M7 has the highest steady melt fraction of λ ss = 0.81 with 107% enhancement among the models having equal volumes of PCM and composite PCM, i.e., M3-M8. The fin-type model M13 and rhombus-type model M14 provide the larger space for enhanced convection that leads to a high steady-state melt fraction values of λ ss = 0.71 and 0.75, respectively. In addition, both AHP and TOPSIS techniques predict model M13 as the optimized choice among all models upon considering the equal weightage criteria for the steady-state melt fraction (λ ss), steady-state time (t ss), and rate of steady latent heat stored per unit cost (L ⁎ ). • Simultaneous charging/discharging of CPCM inside triplex-tube is studied. • Circular, segmented, fin-type, and rhombus-type filling of CPCM are compared. • Melt fraction, melting time, and latent heat storage at thermal equilibrium are presented. • System is optimized by multi-criteria decision making techniques (AHP and TOPSIS). [ABSTRACT FROM AUTHOR]

Pathological detonations are detonations with a propagation velocity higher than the classical Chapman–Jouguet velocity and which depends on the wave structure. Such a behavior has been experimentally observed in low-pressure hydrogen-chlorine mixtures and important discrepancies were reported between the experimental and the theoretical velocities. Using the steady planar detonation model, along with a state-of-the-art chemical mechanism this work aims at investigating two aspects potentially responsible for these discrepancies: (i) the impacts of uncertainties in chemical kinetics mechanisms, and (ii) thermal non-equilibrium effects. The uncertainties in the rate constants of reactions R2: 2Cl+M=Cl 2 +M and R3: Cl 2 +H=HCl+Cl are found to be the dominant sources of uncertainty for the steady propagation velocity and the induction length of the pathological detonations. The multi-temperature, thermal non-equilibrium model is found to provide generally higher detonation velocity than the experimental value and the eigenvalue solutions obtained under thermal equilibrium. Nevertheless, for specific values of the initial vibrational temperature of HCl, the results can be closer to the experimental values. This latter aspect provides the motivation for future work that relies on more comprehensive thermal non-equilibrium modeling. [ABSTRACT FROM AUTHOR]

Logging tools are essential for high-temperature downhole oil exploration. Passive thermal management has been widely used to ensure the normal operation of downhole electronics. A key requirement for passive thermal management is the quick on-site prediction of real-time logging tool temperature. This is challenging due to variable downhole environments, initial temperature distributions, and power dissipations of heat sources. To address this issue, a transient thermal model for predicting the real-time temperature of logging tools is proposed. This model is based on a thermal network model with a discrete thermal equilibrium equation and considers heat transfer processes inside and outside the logging tool. The proposed model considers both the accuracy and the efficiency of prediction and can be applied under different working conditions. The average relative error between the proposed model and the experiment is only 6.5 %. In addition, the computing time and resources of the proposed model are significantly reduced compared with traditional numerical simulations. The proposed prediction model shows promise for wide use in real-time logging tool operations. • A real-time temperature prediction model for downhole electronics was proposed. • The accuracy of the proposed model was verified by the experiment. • The proposed model possessed high computational efficiency. [ABSTRACT FROM AUTHOR]

In order to study the impact of different influencing factors on the active cooling effect of electromagnetic rail. The effects of the flow velocity of cooling medium, the geometric shape of the cooling channel, the cooling water inlet temperature and the nanoparticle mass fraction on the cooling effect of rail are experimentally investigated. The results indicate that increasing the flow velocity of cooling medium can enhance the heat transfer effect. But when the flow velocity exceeds 2 m/s, further increasing the flow velocity has little effect on enhancing heat transfer, and the correlation between the Nusselt number and the Reynolds number has been obtained and expressed as Nu = 0.316 Pr 1 / 3 Re 0.530. Among the three cooling channel geometries studied in this article, square channel has the best cooling effect. The inlet temperature of cooling water has little effect on the convective heat transfer coefficient, but has a significant impact on the thermal equilibrium temperature of the rail. The mass concentration of nanoparticles has a significant impact on the cooling effect of the rail. The larger the mass fraction of nanoparticles, the greater the convective heat transfer coefficient, and the lower the rail peak temperature after reaching thermal equilibrium. However, if the concentration of nanoparticles continues to increase, the effect of enhancing heat transfer will gradually weaken. [ABSTRACT FROM AUTHOR]

Heat conduction in heterogeneous solid mixtures is a crucial problem across various engineering domains. There are two types of assumptions to build the heat conduction model for such mixtures, local thermal equilibrium (LTE) and local thermal non-equilibrium (LTNE). However, a general model works for both LTE and LTNE models for different mixture structures is still to be developed. In this research, we propose a flexible heat conduction model for two-phase solid mixtures under both LTE and local thermal non-equilibrium (LTNE) conditions. The model innovates by introducing an effective volume fraction that aligns with the heat flow direction, eschewing the need for empirical quantities. Our research demonstrates that the LTE model can be directly derived from the LTNE model when constituential temperatures are equal, ensuring methodological consistency. Four mixture structures are numerically analyzed using the finite difference method, validating the model's predictive accuracy and computational efficiency. It is shown that this general heat conduction model offers an effective approach to analyzing heat transfer behavior in different types of two-phase solid mixtures, and it can be extended to multi-phase problems. [ABSTRACT FROM AUTHOR]

Characterization of the onset of combustion reactions within organic materials, such as the tobacco in tobacco products, is very complex. Such materials are commonly used as a porous matrix and the combustion reactions, if present, are generally heterogeneous in nature and compete with drying, vaporization, endothermic and exothermic pyrolysis, as well as assisted exothermal degradation. Fundamental approaches towards the characterization of the onset of combustion reactions are not well established and therefore the literature only provides information that can be used as signatures that aim to reflect the presence or absence of a combustion reaction. These signatures many times link characteristic emissions to specific temperature bands in the organic material assuming local thermal equilibrium between solid and gas phases. This paper presents a review of the literature that reports on the characterization of ignition of heterogeneous combustion within porous combustible materials and the processes commonly associated with thermal degradation and combustion. The review covers emissions and other signatures that aim to establish the onset of heterogeneous combustion, and while the discussion remains general, this review focuses on the evidence that serves to differentiate thermal degradation from the onset of combustion of tobacco products. The literature shows consistency in that below a characteristic temperature of 400 °C, thermal degradation of the tobacco in tobacco products is net endothermic, the formation of products that can be related to oxidation is limited, yields of polycyclic aromatic hydrocarbons (PAHs) are negligible and atmospheric oxygen has very limited influence on the degradation chemistry. Furthermore, the reactions leading to the conversion of PAHs into soot do not occur until much higher temperatures. Therefore, the characteristic signatures associated to the effluent released below a characteristic temperature of 400 °C consist of gaseous compounds and liquid droplets. These liquid-based aerosols are fundamentally different from the carbonaceous soot particles that represent a characteristic signature of combustion. Moreover, an extensive review of the effluent of heated tobacco products during operation establishes that the effluent exhibits the signatures of liquid-based aerosols and does not show the characteristic signatures of combustion processes. • This paper reviews the literature that characterizes the onset of combustion reactions within organic materials, such as the tobacco in tobacco products. • Literature review on fundamental approaches towards the characterization of the onset of combustion reactions. • Information that can be used as signatures that aim to reflect the presence or absence of a combustion reaction. • Signatures that many times link characteristic emissions to specific temperature bands in the organic material are presented. • The review covers emissions and other signatures that aim to establish the onset of heterogeneous combustion, and while the discussion remains general, this review focuses on the evidence that serves to differentiate thermal degradation from the onset of combustion of tobacco products. [ABSTRACT FROM AUTHOR]

Schwarz crystals with uniformly distributed twins enclosed by general grain boundaries (GBs) resembling triply minimal-surfaces were observed in high stacking fault energy metal Pt which is believed not readily to twin. By refining the grains of pure Pt from 140 μm to several nanometers via plastic deformation technique, deformation twins were found to emerge numerously and the structural morphologies of Schwarz crystals can be identified at grain sizes below 4 nm. Both experiments and atomistic simulations suggest that Pt Schwarz crystals are thermally stable at temperatures approaching the thermal equilibrium melting point. The measured room temperature microhardness as a function of grain size, on the other hand, may increase monotonically up to 12.9 GPa, revealing a sustained Hall-Petch relationship. The observed outstanding mechanical stabilities can be attributed to that, regardless of the critical twin size and the stacking fault energy of the material, the plastic deformation at the grain size limit is solely limited by twinning and both the nucleation and bowing-out of twinning partial dislocations from GB sources are notoriously difficult according to simulations and theory. [Display omitted] [ABSTRACT FROM AUTHOR]

• Porous tubes mimicking porous media were developed for gas temperature measurement. • Uncertainty quantification for the method was evaluated with heat transfer model. • The method is effective for the simultaneous measurement with acceptable error level. • The thermal equilibrium state was determined by the proposed method. • The homogenous/heterogenous combustion regime was determined by the proposed method. Simultaneous measurement of gas and solid temperatures in porous media is crucial for phenomenological determination of gas-solid thermal equilibrium state and homogenous/heterogenous combustion regime. Yet, it has remained an unsolved challenging issue for porous media temperature measuring techniques including thermocouple, thermal infrared photography, and X-ray computed tomography. In this work, a simple and convenient method using thermocouples and porous tubes was proposed for simultaneous measurement of gas and solid temperatures in porous media. A variety of experiments with three porous media (steel, sand and biomass), three particle sizes (5 mm, 10 mm, and 15 mm), and three air flow velocities (2.95 cm s −1, 5.90 cm s−1, and 14.88 cm s −1) were conducted to examine the effectiveness and capability of the proposed method. Uncertainty quantification for measuring gas temperature in inert porous media using porous tubes was elucidated with experiments and heat transfer models. Simultaneous measurement uncertainty due to radial deviation of gas and solid measurement locations was also evaluated. It was demonstrated that the proposed method was effective for simultaneous measurement of solid and gas temperature in porous media with acceptable error level (Normalized Root-Mean-Square Deviation, NRMSD = 0.02 – 0.09). Besides, case studies showed that the proposed method was capable to provide valuable experimental data for phenomenological determination of the thermal equilibrium state and the homogenous/heterogenous combustion regime. [Display omitted] [ABSTRACT FROM AUTHOR]

Regenerator characteristics play a pivotal role in shaping the overall performance of Stirling engines. To refine the thermal and flow characteristics of regenerators and elevating the overall output efficiency of engines, this study introduces an innovative design concept for inclined-flow regenerators, where the gas flow direction is inclined to the matrix surface. A novel inclined-flow segmented miniature-channel regenerator, incorporating miniature-channel structures, was fabricated on the basis of this concept. A comprehensive investigation, spanning both component and system levels, was undertaken for scrutinizing the localized distribution and dynamic responses of flow and heat transfer within this regenerator, elucidate the mechanisms through which the regenerator influences engine performance, and compare its efficacy with that of cross-flow and parallel-flow regenerators. The findings underscore that the inclined-flow miniature-channel regenerator attains a harmonious equilibrium in thermal and flow characteristics. Equipping engines with this regenerator yields a notable 325% surge in output power and a 127% boost in thermal efficiency compared to cross-flow regenerators. Furthermore, it demonstrates a 3% increase in output power and a 171% enhancement of thermal efficiency than parallel-flow regenerators. These results affirm the feasibility of the presented concept for inclined-flow regenerators and the constructed inclined-flow miniature-channel regenerator in augmenting Stirling engine performance. [ABSTRACT FROM AUTHOR]

• A new lattice Boltzmann model for thermoplastic composites with heat generation. • Phase transition and local temperature difference under LTE and LTNE are compared. • Effects of heat generation, interfacial heat exchange, matrix fraction are studied. • Dynamic heat generation in thermoplastic composite is a critical LTNE mechanism. • A high internal heat generation enhances the phase transition and LTNE effects. Under the excitation of external fields, fiber reinforced thermoplastic (FRTP) composites can be thermally processed due to the internal heat generation, in which the local thermal non-equilibrium (LTNE) can be significant during the phase transition. In this study, a representative elementary volume scale Lattice Boltzmann model was developed to simulate the phase transition process of FRTP composites with the temperature-dependent internal heat source. The results from LTNE model and local thermal equilibrium (LTE) model were compared in terms of the phase interface evolution and the local temperature difference between fibers and matrix, so that the LTNE effects on phase transition behaviors were examined with different material properties and internal heat sources. It is found that the LTNE effects cannot be ignored in FRTP composites, and the main mechanisms include the dynamic local heat generation, endothermic phase transition of matrix, and relatively high thermal conductivity of fiber. A small heat exchange between the fibers and matrix results in a large local temperature difference and a slow phase transition. A high internal heat generation enhances the phase transition and LTNE effects, but an increase in the temperature range for heat generation leads to a slow phase transition with slight change in LTNE effects. With the increase of matrix fraction, LTNE effects first increase and then decrease due to the combined results of the more internal heat generation and the increase of endothermic mass of matrix and the less heat loss through fibers. This study is significant for guiding the reliable thermal processing of FRTP composites in emerging industrial applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel instrument for thermodynamic evaluation of nanofluids has been created. • A novel characteristic regarding thermal equilibrium time is investigated for evaluation. • MWCNTs, MgO, and BN are utilised in synthesising ternary and binary nanoparticles. • MWCNTs–MgO–BN ternary nanofluids achieved the highest thermal effectiveness. • The thermophysical behind the created instrument has the potential to be a fundamental reference for nanofluid analysis. Nanofluids enhance thermal energy transfer in energy storage applications. Proper nanoparticles are crucial, especially regarding their thermophysical properties. This work fabricated a novel instrument to evaluate a mixture of distilled water-based ternary and binary nanofluids. This work prepared novel ternary and binary nanofluids by mixing multi-wall carbon nanotubes (MWCNTs), magnesium oxide (MgO), and boron nitride (BN) into distilled water at various volume concentrations. The instrument that has been fabricated measures the time taken by the nanofluids to reach a thermal equilibrium state as a new characteristic to evaluate and compare the thermal potential of nanofluids, which alleviates the dependence on other instruments that are occasionally inaccessible or costly for researchers. Thermodynamically, this instrument enables the assessment of nano-energy, manifested as the heat transferred to the nanofluid while reaching an equilibrium state. The results verified the purpose of the proposed instrument; the novel characteristic was affected perfectly by increasing the volume concentration of the nanoparticles in the base fluid. All nanofluids prepared with a concentration of 0.5 % emerged as the most effective in achieving thermal equilibrium in a shorter time than the other concentrations. The ternary hybrid nanofluid MWCNTs–MgO–BN with a volume concentration of 0.5 % had the shortest thermal equilibrium time, 157 s. MWCNTs–MgO–BN ternary hybrid nanofluids transferred 8.3, 5.8, and 11.8 % more heat than MWCNTs–MgO, MWCNTs–BN, and MgO–BN binary hybrid nanofluids. The thermophysical essence behind the result obtained by the created instrument lies in the fact that it generated a new approach to evaluating the nanofluids, thanks to which it was possible to evaluate and find out which fluid has the highest thermal conductivity. The uncertainty analysis showed error acceptability in the experimental instrument, with an average uncertainty value percentage for all presented composites of ± 0.936 %. [ABSTRACT FROM AUTHOR]

This work explores theoretically the gas phase oxidation of allyl methyl sulfide (AMS, H 2 C CHCH 2 SCH 3) initiated by •OH radicals, focusing on the H-abstraction pathway at the M06-2X-D3/aug-cc-pVTZ and MN15/aug-cc-pVTZ levels of theory ( m06Tz and mn15Tz ). The formation of a prereactive complex (PRC) is involved in H-abstraction processes with two potential directions of approach for the OH radical, denoted as "α" and "β". The PRCs, demonstrate increased reactivity, primarily due to the interaction between the sulfur atoms and the hydroxyl hydrogen. A scheme for the H-abstraction mechanism that supports the experimentally identified products and predicts the formation of some S-containing low volatility products is proposed. The comparison of the potential energy surface (PES) between the double bond addition and H-abstraction paths in the AMS molecule shows that at the m06Tz level of theory, the H-abstraction on C3 and the addition to C1 have nearly the same profile of energy, while at the mn15Tz level, the minimum energy channel is the addition to C1. The theoretical rate coefficient for each reaction channel was calculated, considering the formation of a PRC prior to reaching the transition state of each channel and assuming thermal equilibrium between reactants and the PRC. The rate constants were calculated in a multi-TS/multi-conformer way at the SVECV-f12/ m06Tz and SVECV-f12/ mn15Tz levels of theory. The SVECV-f12 method is consistent in its predictions in both systems and exhibits only minor deviations from the experimental rate constants. Despite some specific differences due to the DFT method supporting the SVECV-f12 calculations, both methodologies predict a significant H-abstraction contribution in the AMS + OH gas phase reaction, which explains the high formation yield for acrolein determined experimentally. [Display omitted] • H-abstraction pathway has a significant contribution in the AMS+OH gas-phase reaction, alongside the addition path. • The addition-abstraction branching ratio was 29 - 71 % at the SVECV-f12 level. • The SVECV-f12 method exhibits minor deviations from the experimental rate constants. • The results explain the high formation yield for acrolein determined experimentally. [ABSTRACT FROM AUTHOR]

In this study, the resonance frequency characteristics of the SparkJet actuator are examined through numerical investigation using modal analysis. First, an eigenvalue problem is established to compute the resonance frequencies of the SparkJet actuator, considering its configuration, boundary conditions and internal physical phenomena. To validate the eigenvalue problem, computational fluid dynamics (CFD) simulation is conducted utilizing unsteady three-dimensional Navier-Stokes equations with plasma energy source term, assuming local thermal equilibrium (LTE). Subsequently, the resonance frequencies are obtained by performing fast Fourier transform (FFT) on the thrust and average pressure data obtained from the CFD. In our investigation of the resonance frequency characteristics, eigenmode decomposition on the pressure contour obtained from the CFD is conducted utilizing the eigenfunctions obtained from the eigenvalue problem and their orthogonality. The eigenmode decomposition enables us to quantitatively evaluate the contribution of each eigenfunction to the thrust. Comparisons between the frequencies corresponding to the eigenfunctions significantly influencing on the thrust and the resonance frequencies obtained by FFT reveal a maximum error of 5.29 % and an average error of 2.35 % Moreover, when the taper angle is relatively large (approximately 45 ∘ or more), eigenfunctions significantly influencing on the thrust can be categorized into two distinct geometric patterns. These physically represent the waves that propagate and reflect in the streamwise or radial direction within the SparkJet actuator. This observation implies that the complex interactions of shock waves within the SparkJet actuator can be reduced to a few waves with simple physical interpretations. This may potentially aid in analyzing the physical phenomena within the SparkJet actuator. [ABSTRACT FROM AUTHOR]

• Thermal modeling of porous fiber composite with compressible fluid is proposed. • Compressive effect of the fluid phase on porous fiber composite is demonstrated. • Effect of heating sources on the thermal behavior of the materials is uncovered. The study of heat transfer behavior in porous fiber composite cylinders is vital for optimizing efficient thermal management, insulation materials, and heating equipment design, with applications spanning fields like materials drying, atomization equipment, and aerospace. However, the existing research in this area faces challenges including inadequate experimental data and a lack of clarity regarding fluid-porous material interactions, particularly under the influence of compressible fluids, which demand a more nuanced investigation. This study has developed a model to depict the unsteady heat transfer behavior of porous fiber composite cylinders containing compressible fluid. Consequently, a momentum equation describing the gradual diffusion of compressible fluid within the porous medium is established based on the Darcy-Brinkman-Forchheimer equation. For the purposes of this investigation, the air is treated as a compressible fluid. Concurrently, the corresponding energy equation is formulated, assuming Local Thermal Equilibrium. Ultimately, the devised model is solved by employing the finite volume method. Additionally, a temperature measurement experiment is designed to furnish boundary conditions and verify the model's reliability. The findings indicate that omitting the influence of compressible fluid yields a maximum predicted temperature deviation of approximately 5.6 K at a heating temperature of 420 K. The temperature deviation gradually expands as the heating temperature rises. Furthermore, the parametric analysis is conducted to investigate the impact of porosity, thermal conductivity, geometric size, and the type of heat source on the non-steady heat transfer behavior of composite cylinders. This novel model contributes to a more accurate prediction of the unsteady temperature distribution within porous fiber composite structure cylinders. [ABSTRACT FROM AUTHOR]

Development of the low-cost, high-efficiency, and durable non-precious metal electrocatalysts for cathodic oxygen reduction reaction (ORR) is of vital importance for fuel cells and metal-air batteries. Herein, the carbon-coated NbC nanoparticles (NbC@C NPs) were prepared using DC arc discharge plasma under a methane atmosphere. Then, the nitrogen-doping was conducted by heat treatment, resulting in nitrogen-doped carbon-coated NbC nanoparticles (NbC@C(N x) NPs). Benefiting from the merit of unique core-shell structure and best synergy between the nitrogen-doped carbon shell and the NbC core, the obtained highest nitrogen-doped NbC@C(N 1.36) NPs showed an onset potential (E onset) of 0.89 V (vs. RHE) and a half-wave potential (E 1/2) of 0.79 V, which are comparable to those of commercial Pt/C (20 wt%) (E onset = 0.90 V, E 1/2 = 0.80 V), and its diffusion-limited current density (J L) of 5.99 mA·cm−2 is even higher than that of commercial Pt/C (5.43 mA·cm−2). Moreover, it exhibited a remarkable long-term durability and impressive methanol resistance than Pt/C catalyst. In addition, the real-time optical emission spectrum (OES) analysis of arc plasma shows that the electron temperature (T e) is 7562.9 K in local thermal equilibrium (LTE) plasma. Therefore, the use of the DC arc discharge plasma method opens a fast and simple way to develop cost-effective and highly efficient non-precious metal catalysts for ORR. [Display omitted] • Prepared NbC NPs using a DC arc discharge plasma method show a core-shell structure. • N-doping induces surface electronic structure modification of the graphitic shell, creating the ORR additional active sites. • The electron transfer number of NbC@C(N x) NPs indicates that the reaction path is close to a 4-electron process. • The energy state of the working arc plasma is diagnosed by means of real-time optical emission spectroscopy. [ABSTRACT FROM AUTHOR]

Kirkendall effect has played an important role in developing the understanding of atomic diffusion and mass transport in solids. In thin films and multilayers, in which the microstructure may be far from thermal equilibrium, behavior of a system can be very different from that of the bulk. Therefore, there is a great need to understand the peculiarities of Kirkendall shift occurring at nanometer or sub-nanometer length scale in such systems. In the present work, Kirkendall shift in thin films has been measured with sub-nanometer accuracy, by making use of x-ray planar waveguide structures. Using this technique, we report an apparently counterintuitive result of Kirkendall shift associated with self-diffusion in nanocrystalline iron. The cavity of the waveguide consists of two layers of iron having different microstructures, separated by a thin marker layer of Ag. Thermal annealing results in shift of the Ag marker towards the Fe layer having a coarser grain structure. The effect is established unambiguously by studying two samples with the order of the two Fe layers reversed, and a third sample with the two Fe layers having the same microstructure. The result can be understood in terms of the difference in the microstructure of the two Fe layers; difference in the grain size and hence different concentration of the grain boundaries in the two layers results in a net mass transfer from one region to the other. [Display omitted] [ABSTRACT FROM AUTHOR]

The mathematical framework of reservoir thermal simulators typically relies on the assumption of local thermal equilibrium (LTE) when modeling energy transport through porous media for petroleum engineering applications, including Thermal Enhanced Oil Recovery (TEOR) processes. The LTE presupposes instantaneous exchange of energy between the injected hot fluids and the reservoir's rock and fluids. Nevertheless, it is essential to acknowledge that LTE's validity becomes questionable in specific scenarios, potentially resulting in an overestimation of oil recovery, e.g., when high fluid velocities arise. Under such conditions, the local thermal non-equilibrium (LTNE) formulation may offer a more accurate representation of the energy transport physics. In this study, we present the physical constraints that must be satisfied for the application of two distinct mathematical formulations (1) the one-equation model for the fluids and rock as a whole (LTE is assumed), and (2) the two-equation model, one equation assigned to the fluids and another one to the rock (pseudo-LTNE is assumed). Such constraints were derived by examining conductive and convective heat transport properties via the theory of the method of volume averaging, specifically applied to an oil-water-gas-rock system at the pore scale. It was found that the one-equation model requires that 18 physical constraints to be satisfied, while the pseudo-LTNE model needs to fulfill 9 physical constraints. A sensitivity analysis was conducted based on factor upon which accumulation, conduction and convection constraint equations depend, aiming to identify the conditions under which LTNE occurs within the porous medium. These influencing factors encompass the characteristic time, the Peclet number, the presence of external heat sources, the distribution of phases at the pore-scale, and the disparity between rock and fluid properties. The combinations of these factors can induce the existence of local thermal non-equilibrium. One significant property is the heat transfer coefficient in the reservoir. We recommend that the pseudo-LTNE approach is reliable as long as the rock-fluid heat transfer coefficients are at least one order of magnitude larger than the fluid-fluid heat transfer coefficients (1000 − 10000 W / (m 3 K) ). Contrarily, the OEM should be employed only when the heat transfer coefficients surpass a threshold value of 10000 W / (m 3 K) . When injector and producer wells are hydraulically interconnected, resulting in heightened fluid velocities, it is encouraged the use of the two-equations model. The predictability and reliability of the energy models were verified by comparison of predicted oil recovery against data from laboratory experiments. The equations presented in this study consistently demonstrate their utility in assessing the reliability of energy transport models for TEOR scenarios. • Energy equations were derived considering the Pseudo-Local Thermal Non-Equilibrium. • Mathematical constraints, to use Pseudo-LTNE were derived. • The conditions at which LTNE is present in an oil reservoir were determined. • An external heat source to the reservoir induces Pseudo-LTNE between phases. • In the steam injection process, the Pseudo-LTNE is present near the steam front. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermalization between the quantum-dot and Mn2+ excited states in InP:Mn/ZnS is fast. • The equilibrium populations depend on the quantum-dot size. • The ratio of the host and dopant radiative lifetimes governs the emission properties. The photoluminescence properties of ZnS-capped Mn-doped InP nanocrystals are shown to be determined by the high ratio of the radiative rate constants of the host and dopant emission, by the polydispersity-induced inhomogeneous broadening, and by the rapid establishment of thermal equilibrium in the distribution of the excitation between the energy levels of the quantum dot and the dopant ion. Because of the combination of these factors, the resulting photoluminescence includes the delayed host fluorescence and the quenched dopant phosphorescence, both having very broad lifetime distributions. [ABSTRACT FROM AUTHOR]

• A novel thermo-electro-elastic model for dielectrics exposed to ultrashort pulsed laser is proposed. • The thermoelastic equations are modified based on the G-L generalized thermoelasticity. • Kinks occur in the transient responses, which is due to the rapid change of reflectivity. • Effects of laser parameters and variable thermophysical properties are analyzed. A novel model involving electron dynamics, electron-lattice interactions, and thermoelastic excitation for dielectrics exposed to ultrashort pulsed laser is proposed. The thermoelastic equations are modified based on the G-L generalized thermoelasticity and consider the temperature-dependent thermophysical properties. An axisymmetric problem of ultrashort pulsed laser irradiation on fused silica is presented. The fully-coupled equations are solved simultaneously using the finite element method to obtain the transient electron density, electron temperature, lattice temperature, and stresses. The evolution of transient responses and the effects of laser intensity, pulse duration, and temperature-dependent thermophysical properties are analyzed in detail. It was found that there are kinks in the distribution of transient responses, which is attributed to the rapid change of reflectivity. The axial stress has wave-like characteristics. The electron temperature is slightly lower than the lattice temperature after the thermal equilibrium is achieved. Maybe the temperature-dependence of lattice thermal conductivity could be neglected to reduce computational expenses. [ABSTRACT FROM AUTHOR]

Electric thrusters are considered to be the most promising propulsion system of choice for space gravitational wave detection. However, the requirement of high accuracy and drag-free control results in significant challenges in thrust measurements. To better understand the thrust noise characteristics, this work proposes a time-frequency-domain method for thrust noise analysis, i.e., a scalogram method attained through wavelet analysis. Unlike the conventional Fourier transform method, it can provide 3-D relationships for the time-frequency and thrust noise. A free-state thrust measurement experiment identified that the environmental temperature produces the dominant impact in the thrust noise. During a 70,000 s measurement, even without thruster operation, the thrust noise increased from 0.3 μN/Hz1/2 to 19 μN/Hz1/2 as the environmental temperature increased from −1 °C to 3 °C. The corresponding frequency of peak thrust noise for the entire period tends to be the same of 0.1 Hz. Additionally, a Hall thruster thrust measurement experiment was conducted to verify the method's time-varying analysis capability for thrust noise. The complete time-frequency thrust noise variation throughout the entire operating process of a Hall thruster was observed. The results at different stages of thruster operation indicate that thrust noise has the greatest influence 150–300 s after ignition. This is because the thrust stand will take hundreds of seconds to reach thermal equilibrium after ignition. Another finding during the Hall thruster operation is that the 0.1 Hz frequency corresponding to the peak thrust noise is highly consistent with the frequency of peak thrust noise in the free-state thrust experiment. This reveals the fact that the 0.1 Hz frequency should be the dominant frequency for thrust noise caused by temperature drift in our thrust measurement system. • A time-frequency-domain method for thrust noise analysis is developed for use with electric thrusters. • Time-varying and non-stationary features of thrust noise are analyzed using wavelet transforms. • The noise at 0.1 Hz is identified as the key frequency of thrust noise caused by zero drift. • Variations in the thrust noise during the entire operation process of a Hall thruster were obtained. [ABSTRACT FROM AUTHOR]

To investigate the envelope radiation characteristic of stratospheric airship, three kinds of airship models with different dimensions (fineness ratio of 3, 4, 5) are selected. After establishing the thermal equilibrium equations of the selected models, the influence of the envelope radiation characteristic on the envelope and airship gas is first addressed to determine the optimal fineness ratio by considering the flight dynamics characteristics. Furthermore, the effects of envelope emissivity, envelope absorptivity, solar cells radiation characteristics, and typical envelope materials on the envelope radiation characteristics of airship are discussed in depth. The results show that: (1) With the assumption of same absorptivity and emissivity, the larger the fineness ratio of the airship, the smaller the diurnal temperature difference of the main helium gasbag, and the better the thermal characteristics of airship as well. When the envelope radiation characteristics vary, the temperature difference of main helium gasbag with a fineness ratio of 4 in one day is always less than 1 K, compared with the fineness ratio of 5. However, the temperature difference of main helium gasbag with a fineness ratio of 3 exceeds that with the fineness ratio of 5, and reaches its maximum of 6 K. Therefore, the fineness ratio of 4 is regarded as optimal by considering the floating constraints of low drag and high buoyancy. (2) In the case of higher long-wave emissivity and lower short-wave absorptivity of the envelope material and solar cells, the diurnal helium temperature difference is the smallest, and the thermal performance of the aerostat is better. (3) Among the five typical envelope materials, i.e., white Tedlar film, white PU film, silver-plated Teflon film, aluminized PET film, and white PVF film, the aluminized PET film is more conducive to controlling the helium temperature difference and reducing the volume change of gasbags. The aforementioned results can provide a theoretical basis for improving the thermal performance of stratospheric airships. [ABSTRACT FROM AUTHOR]

Mayenite electride has attracted increasing research interests because of its unique electronic properties. The thermionic emission behavior of the mayenite electride is relatively unknown. Previous studies revealed that mayenite electride exhibited a bare work function ranged from 2.1–2.6 eV when the thermionic emission was tested in vacuum, and enhanced emission currents could be achieved by applying a super-high external electric field. In this paper, the thermionic emission behavior and the corresponding effective work function of two types of mayenite electride based composites, mayenite electride-titanium and mayenite electride-carbon, were investigated in an Ar glow discharge plasma at elevated temperatures (400–1000 K) without applying a high external electric field, which is critical for the application in electric propulsion and other aerospace apparatus, yet never had been done before. During the testing, the thermal equilibrium process and plasma sheath expansion were observed. The effective work function of the two mayenite electride composites were determined as a function of temperature. The Rasor-Warner model was applied to determine the bare work function and adsorption-site density of the mayenite electride based composites. Results suggested that the adsorption of Ar ions led to the enhanced thermionic emission (~30 A/m2 at 985 K) and low effective work functions (0.9–2.2 eV) of mayenite electride based composites, without the need of applying high electric fields. Our findings will pave the ways for the application of mayenite electride and its composites as the thrust cathode materials for electric propulsion where plasma is present. [ABSTRACT FROM AUTHOR]

Light element solutes such as carbon (C), nitrogen (N), and oxygen (O) are impurities commonly seen in tungsten alloys, often exerting great impact on materials properties due to their strong interaction with defects. In this work, we conducted a comprehensive investigation into the atomistic properties of small vacancy-impurity defect complexes in tungsten using rigorous first-principles calculations. Through the integration of a statistical approach, we meticulously examined the concentration distributions of these complexes across various temperatures and impurity concentrations. Our findings reveal that the introduction of C/N/O impurities significantly augments the concentration of vacancy-type defects to a level well above the thermal equilibrium vacancy concentration in pure tungsten. Moreover, we conducted a thorough assessment of the diffusivity of C/N/O atoms, conclusively demonstrating that the inclusion of the vacancy trapping effect is paramount in comprehending their unexpectedly low diffusivity observed in experiments. Finally, in conjunction with an object kinetics Monte Carlo method, we revisited the experimental determination of the divacancy binding energy in tungsten. We showed that the presence of C/N/O impurities may have conceivably impacted the experimentally ascertained divacancy binding energy. This work provides accurate data on evaluating vacancy-impurity interaction in tungsten, unveils the pivotal role played by C/N/O in affecting vacancy concentration and divacancy binding energy, and sheds new insights toward understanding the diffusion behavior of impurities in tungsten. [Display omitted] [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) of composition-sensitive NiTi shape memory alloys (SMAs) is hindered by uncontrollable non-equilibrium microstructures, leading to functional performance degradation and limitations in high-throughput net-shaping applications. To address these challenges, we propose a novel approach combining annular intra-laser directed energy deposition (AIL-DED) with a tailored gradient post-treatment process. This enables the fabrication of nanocomposite microstructures in NiTi SMAs with precise control over the homogenization of Ti 2 Ni nanoprecipitates. In-situ monitoring and characterization of thermal history, microstrain, and constitutional phases, were utilized to uncover the relationship between multi-scale structural features and mechanical responses. The interplay between laser reflectivity, energy input, and lattice thermal vibrations affects forming quality in AIL-DED. Dynamic temperature variations were studied before reaching thermal equilibrium, revealing insights into thermal and mechanical interactions during the process. These findings contribute to understanding challenges in fabricating high-quality NiTi SMAs. Examining phase transformation behavior and its correlation with processing parameters deepens understanding of microstructural evolution and provides insights for tailoring material properties. The stress relaxation and dislocation evacuation at elevated temperatures caused the expansion of lattice and interplanar spacing in the age-treated SMA's B2 matrix phase, exhibiting a stable two-step phase transformation behavior (B19′↔R↔B2). AIL-DED combined with two-stage heat treatment strategy demonstrated enhanced homogeneity of non-equilibrium microstructures, resulting in the formation of high-density, well-dispersed Ti 2 Ni nanoprecipitates, with a semi-coherent interface to B2 matrix. The combination of load-bearing strengthening through well-dispersed Ti 2 Ni nanoprecipitates and Orowan strengthening at the semi-coherent interface yielded simultaneous enhancements in nanohardness, ultimate compressive strength, compressive fracture strain, and deformation recovery, following the AIL-DED combined with two-stage heat treatment process. The fracture mechanism transitioned from a mixture of brittle-ductile behavior to predominantly ductile characteristics. This study provides valuable insights that advance additive manufacturing and enhance the functional performance of SMAs in critical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• Buckling and postbuckling of FG-GOEAM plates under high-temperature biaxial compression are investigated. • Thermal buckling and postbuckling of FG-GOEAM plates under uniform thermal loading are investigated. • The explicit expressions of the mechanical and thermal postbuckling problems of FG-GOEMA plates satisfying both the governing equations and the boundary conditions in an asymptotic sense are given. Postbuckling under high-temperature biaxial compression and thermal postbuckling under uniform thermal loading of functionally graded (FG) graphene origami (GOri)-enabled auxetic metamaterials (GOEAMs) plates are investigated. The plates consist of multiple layers of GOEAMs with varying levels of GOri content in the layers across the direction of the thickness. The nonlinear governing equations of the plate are based on the first-order shear deformation theory (FSDT) and the von Kármán type nonlinear strain–displacement relationship. The mechanical and thermal postbuckling equilibrium paths of FG-GOEMA plates on the elastic foundation are determined using the two-step perturbation method. The effects of the elastic foundation, temperature, GOri content, GOri distribution pattern, and degree of GOri folding on the mechanical and thermal postbuckling of FG-GOEMA plates are discussed. [ABSTRACT FROM AUTHOR]

• The interaction of two collinear interface cracks in TBCs is investigated. • The ramping time of imposed thermal loading is considered. • According to the maximum hoop stress criterion, higher fracture risk occurs with the approaching of collinear interface cracks. Ceramic based thermal barrier coatings are extensively employed to shield critical engineering components from harsh temperature environments, where the typical Fourier's law may not be able to provide an accurate assessment of the physical process. This work adopts a more generalized heat conduction approach to reveal the thermal and fracture interaction mechanism of two collinear interface cracks in orthotropic functionally graded thermal coating systems by dual-phase-lag theory. The heating rate of the imposed thermal loading on the exterior bounding surface is modeled by ramp-type function, where the ramping period is comparable to the certain time spent for building the local thermal equilibrium within composites. The methods of Fourier transform and Laplace transform in conjunction with the singular integral equations are applied to solve the complex transient thermoelastic problem. Parametric investigations are conducted to investigate the impacts of ramping time, thermal lags, nonhomogeneous parameters, and crack spacing on the thermal and fracture characteristics. According to the maximum hoop stress criterion, higher fracture risk is discovered with the approaching of collinear interface cracks. [ABSTRACT FROM AUTHOR]

We show that the minimal Type-I Seesaw mechanism can successfully account for the observed dark matter abundance in the form of a keV sterile neutrino. This population can be produced by the decay of the heavier neutral leptons, with masses above the electroweak mass scale, while they are in thermal equilibrium in the early Universe (freeze-in). Moreover, the implementation of the relevant phenomenological constraints (relic abundance, indirect detection and structure formation) on this model automatically selects a region of the parameter space featuring an approximate lepton number symmetry. [ABSTRACT FROM AUTHOR]

The entrainment defects generated during the preparation of semi-solid slurries following the rheocasting technique impart poor mechanical and comprehensive properties to the casting. However, the mechanism of formation of these defects in semi-solid slurry has rarely been studied, so the mechanism of the formation of entrainment defects in the semi-solid A356 aluminum alloy be herein reported. The speed of the thermal equilibrium body (TEB) was maintained at 1300 and 2500 rpm where the entrainment defects of slurry were analyzed under conditions of internal cooling thermal equilibrium (ICTE). Results obtained using the SEM and computed tomography revealed the formation of bifilm defects, bubble trails, gas pores, and shrinkage pores in the slurry produced when the speed of rotation was 2500 rpm which resulted in lower elongation. The tensile specimens fabricated at the 2500 rpm speed were worse than those fabricated when the rotational speed was 1300 rpm in the aspect of elongation and reliability of mechanical properties. Results from numerical simulation and water simulation indicated that the phenomenon of surface turbulence promoted the formation of entrainment defects, and the bubbles entrapped inside the slurries could not escape according to the bubble theory floating calculation. • Extensive and dispersed gas pores and shrinkage defects are found in the selected samples fabricated at 2500 rpm, as shown in Fig. 4a and 4b. As Fig. 4c reveals that the shapes and sizes of gas pores and shrinkage defects are clearly different from each other. • Fig. 5 presents a typical bifilm defect with its crack-like characteristics, which form an irregular shape due to its continuous folding, and this feature can be used to distinguish it from the stress-induced crack morphology. • Results from numerical simulation and water simulation indicated that the phenomenon of surface turbulence promoted the formation of entrainment defects, and the bubbles entrapped inside the slurries could not escape according to the bubble theory floating calculation. [ABSTRACT FROM AUTHOR]

Accurate results for fluids at thermal equilibrium, valid both outside and inside the critical region, are difficult to obtain due to the singular nature of this region. However, for simple models like interacting hard spheres and the Ising model high accuracy has been obtained by use of SCOZA (self-consistent Ornstein-Zernike approximation). Here this approach is extended to one component fluids more generally. Outside the critical region good analytic approximations may be obtained by use of statistical mechanical results that are adjusted to experimental data and/or computer simulations. However, such approximations typically will be of mean field type in the sense that the usual singular behavior in the critical region and in the transition to it, is not present. Here the SCOZA is generalized such that approximations accurate outside the critical region are utilized as basic input in the SCOZA problem. The singular behavior is connected to correlations of increasing range that develop as the critical point is approached. These correlations contribute both to the internal energy and compressibility of the fluid, and they give another contribution to the SCOZA partial differential equation. Accurate results in the critical region are expected to be obtained by adjusting one or a few parameters. • The SCOZA is extended to fluids more generally. Earlier it was developed to improve upon the MSA. • By this extension also equations of state known well outside the critical region, can be input to the SCOZA problem. • The SCOZA gives a rather accurate description of the critical region with its singular behavior. • Solution of the SCOZA problem is expected to give accurate results also in the critical region for the fluid of interest. [ABSTRACT FROM AUTHOR]

This study involves an investigation on fully evaporation process inside annular porous heat exchanger using Cu/distilled water nano-fluid. Emphasis has been placed on how the use of Cu/distilled water affected two-stage flux predictions. Two-phase mixture model, based on the considerations of Local Thermal Equilibrium (LTE), has been reformulated to involve the influences of employing nano-fluid instead of only water. To display the actions of employing nano-fluid, the predictions of liquid saturation and temperature, obtained using Cu/distilled water and only water, have been presented and compared for a wide ranges of geometric conditions, operating conditions and properties of porous media. The outcomes displayed that the using Cu particle to water has a large impacts on the heat diffusivity, where the boiling and condensation fronts are considerably moved to downstream and upstream sections, respectively, as compared to the predictions of only water due to rising the axial diffusion. The temperature at the pipe exit is considerably decreased when adding Cu particles to water as compared to the pure water case. The predications of Cu/distilled water show that the nano-fluid volume fraction, geometric parameters, operating parameters and porous structure properties have high actions on the locations of initiation and termination of phase change process. Since the fluid temperature for pure water case is extremely high at the superheated vapour region, the addition of Cu particles to water considerably reduces the fluid temperature in this region and hence, the use of nano-fluid can be considered as a safety factor in the applications that used heat exchangers (boiling processes) due to it improves the mechanism of heat transfer during the boiling process. [ABSTRACT FROM AUTHOR]

• Use of three optical techniques to evaluate thermal-hydraulics in LOCA conditions. • Analysis of the blockage ratio effect on the cooling phase and on the droplets. • The Leidenfrost temperature is highly dependent on the droplets kinetic energy. • Droplets diameter reduces downstream of the heated tube due to evaporation or break-up. • Valuable data for the validation of mechanistic models are provided. During a Loss of Coolant Accident (LOCA) in a Pressurized Water Reactor, partial or complete drying of fuel assemblies may take place. In these conditions, the fuel temperature increases and may lead to substantial deformation of the fuel rod cladding and a partial blockage of the fluid sub-channels. These regions could significantly affect the cooling capacity of the nuclear core during the reflooding phase by the emergency core cooling systems. Understanding the cooling process and the thermal-hydraulic characteristics of the flow in these deformed regions is decisive to guarantee nuclear safety. Looking to provide valuable experimental data to validate existing and new models, this work is an experimental study on the thermal hydraulics during the cooling of a vertical tube with an internal steam-droplets flow, representing the LOCA conditions at sub-channel scale. The effect of the blockage ratio on the tube temperature, heat dissipation, wall rewetting, and droplets characteristics is evaluated by testing three configurations (0%, 61% and 90%). Optical techniques were used for a comprehensive characterization of the process, being them infrared thermography, phase-Doppler analyzer and three-color laser induced fluorescence thermometry. In general, wall rewetting in the test section occurs from bottom to top, although there is a discontinuity in the rewetting front with the 90% blockage ratio configuration. The droplets diameter reduces downstream of the test section because of evaporation. Droplets breakup was specifically observed with 90% blockage ratio. In all the cases, the droplets temperature was approximately the same up- and downstream of the test section, which indicates they are in nearly thermal equilibrium state and, therefore, representative of a LOCA situation. [ABSTRACT FROM AUTHOR]

In order to investigate the influence of the inductor position on thermal characteristics during induction lap welding (ILW) process of steel-aluminum heterogeneous metals, the finite element model of ILW process was established. The effect of X-coordinate and Z-coordinate on the magnetic flux density, heat affected zone (HAZ) and temperature uniformity during ILW process was studied. The results show that a relatively small Z-coordinate value increases the maximum magnetic flux density and the maximum temperature of the workpiece in the process of ILW on Fe/Al dissimilar metal, reduces the time to reach the thermal equilibrium, and the temperature uniformity is relatively low. A relatively small X-coordinate value reduces the maximum magnetic flux density and the maximum temperature of the workpiece in the process of ILW on Fe/Al dissimilar metal, increases the time to reach the thermal equilibrium, and the temperature uniformity is relatively high. The Z-direction coordinate value (change of proximity effect) has a greater influence on the electromagnetic and temperature fields during ILW than the X-direction coordinate value (change of magnetic shielding region). The simulated temperature curve with time and the HAZ distribution under different process parameters agree with the experimental results, which proves the reliability of the numerical model. [ABSTRACT FROM AUTHOR]

In this study a 2D two-temperature chemical non-equilibrium model is established to investigate the flow characteristics and chemical reactions processes around hypersonic inflatable reentry vehicle at different flight altitudes and reentry velocities. This chemical kinetic model is based on the Gupta model and modified by comparing the species mole fractions at thermal equilibrium condition with the results obtained by Saha equation. In order to validate the model, the calculations are performed for a blunt cone ELECTRE and a cylinder, the predicted heat flux and pressure are compared with experimentally measured data and the maximum differences on heat flux and wall pressure are less than 20% and 5%, respectively. Then the flow characteristics behind the shock wave and wall heat flux are discussed in detail for Titans vehicle. It is found that the pressure declines with the increase of altitude and reentry velocity, this variation trend is opposite to the wall heat flux, whose maximum value increases from 58 kw/m2 to 107 kw/m2 with the rise of flight altitude from 79 to 88 km due to the large temperature and component gradients. This indicates that the aerodynamic force and heat flux should be taken into account simultaneously for the design of inflatable reentry vehicle. By analyzing the chemical reactions processes behind the strong shock wave, it is seen that not only the dissociation reactions of N 2 and O 2 molecules play an important role, but also the neutral species exchange reactions contribute to the density change of species. The dominant ionization reactions are N+O→NO++e and NO+M → 4 NO++e+M 4 , while the ionization processes are weak, and the maximum ionization degree is smaller than 1%. The analysis of dominant chemical reactions can provide a reference for the numerical modeling study of hypersonic reentry vehicle. [ABSTRACT FROM AUTHOR]